Conventionally there have been known a power transmitting device contactlessly transmitting electric power and a power receiving device contactlessly receiving electric power. For example, U.S. Patent Application No. 2011/0074346 (PTD 1) describes a wireless power transfer device including a coil and a lid member covering the coil and having a temperature sensor attached thereto. When a foreign matter exists near the coil and serves as a cause to generate heat, the above configuration allows the presence of the foreign matter to be sensed.